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Just thought I'd post with a heads up that I discovered with my tank.
I just got an order from Premium Aquatics (love those guys) with a refractometer among the items. With my old floating glass tube hydrometer the salinity was reading right at 1.025 but with the new refractometer its showing 1.030 :eek:
I'm slowly removing water from the tank and letting my auto-top off refill with fresh water which should bring the salinity down.
 

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Yup , that's what a lot of people find,,i had three swing arm hydro's and ALL of them were off and inconsistant,,ya just gotta remember to make sure the refracto and the water are pretty much the same temp (ambient),,,and that the refracto is calibrated,,,,
 

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Yup, Premium is TOP NOTCH!:beer: :beer:
 

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Same deal here, I couldn't belive the true salinity I was at when I got the refractometer.
 

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do the cheap ones always read low? I bought a refractometer last month in a club deal, my old cheap one was reading 1.024 and the refractometer reads 1.028. After its calibrated with ro water how do you check the accuracy of a refractometer?
 

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Joel said:
After its calibrated with ro water how do you check the accuracy of a refractometer?
You could compare readings with someone elses. My cheap plastic box hydro, which I had been using for over five years, was so far off from my refractometer that I was reluctant to adjust the salinity. So I did it veeeery slowly.
 

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Yup, i even had all three of my swing arm hydro's calibrated/marked at Harbor once using a Refractometer,,they ALL were inconsistent on readings,even after marking ".025" on them.the $$i spent on swing arms over the years , i coulda bought a refracto sooner,,,,
 

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If your refractometer is an automatic temperature calibrated version, you shouldn't look at the S.G. scale. This will only give the S.G. if your sample was the same temp as the reference. (If it's the d20/20 reference as usually denoted by the scale, the reference is a 68 deg F sample.) The ATC mechanism (metal strips that expand/contract with temp) will shift the scale so that the S.G. corresponds to what it would be at 68 deg F. However, the actual S.G. of your sample will vary since it will (hopefully) be warmer. (The S.G. will actually be lower since warm water is less dense.) This explains why you are reading S.G. measurements considerably higher than your hydrometers.

For ATC, look at the salinity scale and shoot for your desired value. (i.e., 35 ppt or whatever you want) This is because salinity (or amount of salt in solution does not vary with temperature.)

For non ATC refractometers, the scale will not shift. You have to account for the temp difference and scale accordingly.

Clayton
 

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Where on their site is this refractometer? I wanted to check it out, but couldn't find it.
 

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i had the same experience my salinity was at 1.025with 2 plastic hydrometers. checked with my new refractometer and its 1.028. i have had very good successs at 1.028 so thats where my tank is staying.
 
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